NOTE-2-9-5

Fixed a bug in cw-gstack that was causing a hard error when attempting
to report on a forced assumption. Thanks to Jared Davis for pointing this
out and sending an example that helped us to determine a fix.

Fixed a bug that broke wet. Thanks to David Rager for bringing this
bug to our attention.

Guard verification now evaluates ground subexpressions (those with no free
variables) when computing the guard conjecture for the body of a function.
Thanks to Jared Davis for useful conversations leading to this change.
See verify-guards, in particular its ``Note on computation of guard
conjectures and evaluation'' near the end of that topic, for more details.

Added a warning when a theory-invariant is redefined. Thanks to Jared
Davis for suggesting a warning in this case and providing an informative
example. Also, theory-invariants are now maintained more completely,
as they are checked at the end of every event except for events executed on
behalf of an include-book or the second pass of an
encapsulate.

Fixed the handling of runic designators to match their specification
(see theories), so that disabling the name of a defthm event
disables all rules generated for that event.

(For those who do numerous builds using feature :acl2-mv-as-values,
currently only OpenMCL and multi-threaded SBCL by default:) You can speed up
builds by adding the following parameter to make, under conditions
described in GNUmakefile: USE_ACL2_PROCLAIMS=:REUSE.

Arranged that traced functions (see trace$) are automatically untraced when
events are undone (for example see ubt), at least for most underlying Common
Lisp implementations.

The macro defun-sk now creates non-executable functions, which allows
stobjs to be used where they had previously been prohibited. More
generally, the user now has control over declare forms to be used by
the underlying defun'd function; see defun-sk. Thanks to Sandip for
pointing out the need for such a modification.

:Definition rules are now treated, at least by default, as truly
first-class definitions. In particular, :expandhints use the
latest :definition rule by default. You may specify
:install-body nil to get the previous behavior of :definition rules;
See definition, and you may choose a previously-installed :definition
rule to provide the current body; see set-body. Also see rule-classes for
details of the :install-body field, and see hints to see a new :with
directive for controlling expansion. The :with directive for :expand
hints can even direct the use of a :rewrite rule for expansion!
Thanks to various people, including Sandip Ray and Rob Sumners, for
discussions on the issue of the applicability of :definition rules for
:expandhints.

Constraints for functional instantiation now use the original definition
rather than a simplified (``normalized'') version of it.

Lemma names in directory books/ordinals have been changed by replacing
/\ with & and replacing \/ with V. We made this change
because backslash is an escape character and hence disappears unless it is
itself escaped.

Fixed proof-tree output so that failed non-proof events do not cause the
proof-tree to be re-printed. Thus for example, if you have already advanced
the checkpoint marker, it will not be reset by subequent failed non-proof
events. Thanks to Pete Manolios and Peter Dillinger for bringing this bug to
our attention.

Fixed a bug that was preventing the printing of stobj fields as
constants instead of numbers in certain cases. (Note that this bug only
affected printing, not soundness.) Thanks to Eric Smith for bringing this
problem to our attention and providing the following example (which now works
fine).

Thanks to Anna Slobodova for bringing this issue to our attention. A related
change is that all arguments of progn must now be embedded event forms
(see embedded-event-form), so use er-progn instead if this is not the
case.

The change to progn mentioned above also fixes a bug in handling
local events inside a progn that is inside an encapsulate or
in a book. For example, the following form formerly caused an error.

We fixed two bugs in :puff and :puff*. The first,
brought to our attention by Eric Smith (who we thank), caused a cryptic error
message when puffing a command with no subsidiary stored events; try, for
example, (encapsulate () (value-triple 3)). The second was due to a
failure to restore the acl2-defaults-table. Suppose for example that
we have certified the book foo.lisp, which contains
(program) followed by some definitions and/or theorems. Now
suppose we start ACL2 and execute the following.

A new event, make-event, provides something like macros that take
state. For example, one can use it to put tests into certified books, do
proof search, and generate new function names. Many examples appear in
directory books/make-event/. See make-event. Thanks to Bob Boyer and
Jared Davis for useful feedback and to Warren Hunt, David Rager, and Sandip
Ray for helpful discussions leading to some of the examples in directory
books/make-event/.

In support of make-event, which is described in the preceding
paragraph, certify-book has a new keyword argument, :save-expansion,
that controls whether the result of expanding make-event forms is
written out to a file. See certify-book; and for a discussion of book
expansion files, see make-event.

We fixed a soundness bug that did not correctly detect local events.
For example, the following event was admitted.

In the course of adding the guard-checking value :none described in
the paragraph above, we eliminated an optimization that eliminated guard
checking for some recursive calls of :logic mode mutually-recursive
functions that have not had their guards verified. But we doubt that this
change will be noticed by any users!)

The ACL2 hyper-card has been enhanced, thanks to David Rager, with a listing
of ``Useful EMACS Commands'' to match comments in emacs/emacs-acl2.el.

Made some improvements to books/Makefile-generic (a file discussed
elsewhere; see book-makefiles). In particular, improved handling of
.acl2 files for dependencies target.

(Only OpenMCL and, with feature :acl2-mv-as-values, GCL) Fixed a bug that
was causing proclaiming to fail when definitions are submitted interactively.

The default stack size has been increased for several lisps.

(Very technical) A restriction has been weakened on the use of localstobjs under a call of an ACL2 evaluator (trans-eval or
simple-translate-and-eval). Now, the error can only take place for
stobj names that occur in the term being evaluated. Thanks to Erik
Reeber for bringing this issue to our attention.

The notion of ``ancestor'' has been changed slightly. This notion is used by
extended metafunctions and break-rewrite (see extended-metafunctions
and see brr@), and also with backchain limits (see backchain-limit and
see set-backchain-limit). Basically, each time a hypothesis is encountered
during application of a rewrite rule, that hypothesis is pushed (after
instantiating and negating) onto the current list of ancestors before it is
rewritten. However, hypotheses of the form (equal var term), where
var is free (see free-variables), had not been included in the ancestors
(similarly for (equiv var (double-rewrite term)) where equiv is a
known equivalence relation). Now such ``binding hypotheses'' are
included in a special way in ancestors data structures. In particular,
(null (mfc-ancestors mfc)) will now be true if and only if the term being
rewritten is part of the current goal as opposed to a hypothesis from a rule
encountered during backchaining, even if that hypothesis is a binding
hypothesis. Thanks to Dave Greve for bringing this issue to our attention.

Termination and induction analysis now continue through both arguments of
prog2$, not just the second. (Normally, the gathering up of if
tests stops at function calls; but it continued through the second argument
of prog2$, and now it will continue through both arguments.) Thanks to
Sol Swords for discussion leading to this change.

The ACL2 distribution is now kept on the http server rather than the ftp
server (but the home page has not been moved). Thanks to Robert Krug for
letting us know that some ACL2 users have found it inconvenient to fetch ACL2
using ftp.

The file books/README.html has been renamed to books/Readme.html,
since some browsers don't show the former in the directory listing.